With Long Term Evolution (LTE) networks being widely deployed, the next performance leap is offered by LTE advanced (LTE-A) networks. The LTE advanced networks use heterogeneous network (HetNet) topology capable of providing higher spectral efficiency per unit area. The HetNet has plurality of network nodes includes macro cell (s), pico cell (s), femto cell (s) and relay base stations which enable flexible and low cost deployment. The HetNet enables a network operator to provide a uniform broadband experience or Quality of Service (QoS) to users anywhere in the LTE advanced network by offloading the users from high power network nodes such as macro cell to low power network nodes such as the pico cell or the femto cell.
These low power network nodes are either served on different carrier frequency or a single carrier frequency. In the co-channel HetNet deployment, all low power network nodes share the same carrier frequency as used by the high power network nodes i.e. macro cell(s). The User Equipments (UEs) within the coverage of one cell experience dominant interference from another overlapping and/or adjacent cell. Such an interference scenario is termed as dominant co-channel interference. The cell in which the UE experiences dominant co-channel interference on the served carrier frequency from a nearby cell is called a victim cell and the adjacent or overlapping cell causing the dominant co-channel interference is called an aggressor cell. The co-channel interference is significant when the UE in connected mode falls within region of inter-cell interference of the victim cell, as the UE experiences lower than usual Signal to Interference plus Noise Ratio (SINR). One or more UEs experiencing dominant co-channel interference in the inter-cell region are called victim UEs. Typically, in the HetNet environment primarily comprising macro cells providing coverage and pico cells overlaid on the macro coverage for offloading purpose on the same carrier frequency, the region of inter-cell interference is pre-dominantly the cell range expansion (CRE) region of pico cells. In such a scenario the aggressor cells are high power macros and the victim cells are low power pico cells.
Similarly, in the HetNet environment primarily comprising macro cells providing coverage and femto cells deployed in residential or enterprise locations providing closed subscriber group (CSG) members radio access on the same carrier frequency, the region of inter-cell interference is pre-dominantly the coverage of the femto cell for a non CSG member. In such a scenario for the non-CSG member UE the aggressor cell is low power femto and the victim is high power macro.
Inter-cell Interference Co-ordination (ICIC) for data channel protection in co-channel HetNet provides mechanism to handle inter-cell interference for connected mode UEs within the CRE region. The ICIC is handled through Time Division Multiplex (TDM) approach based on Almost Blank Subframe (ABS) based on Third Generation Partnership Project (3GPP) Release 10 LTE-Advanced specification. Subframes with reduced power on some physical channels and/or reduced activity are characterized as ABS. Typically, the aggressor cell employs ABS such that the data channel scheduled to the victim UE by the victim cell is protected during ABS. Hence, the victim UE does not experience interference from the dominant interferer cell during ABS. According to 3GPP Release 10 LTE-Advanced specification, when TDM ICIC is implemented by means of ABS, the serving cells derive UE specific measurement resource restriction patterns based on the ABS and configure them to the respective victim UEs. The configured victim UEs perform restricted measurements, specific to subframes that are identified based on the configured measurement resource restriction patterns.
In connected mode, the UE is supposed to maintain up-to-date system information (SI) comprising the Master Information Block (MIB), type one System Information Block (SIB-1) and type two System Information Block (SIB-2). According to the 3GPP specification, whenever the system information changes the UEs are notified through a paging message. According to 3GPP specification TS 36.331, UE acquires the required system information from the beginning of the successive Broadcast Control Channel (BCCH) modification period following the current BCCH modification period in which the system information change notification was received. The system information to be acquired is the legacy MIB and/or the legacy SIB-1. Then, depending on the systemInfoValueTagfield in the legacySIB-1, the UE decides which other SIBs the UE has to acquire.
However, the legacy MIB transmission is fixed in time and frequency. The legacy SIB-1 transmission is fixed in time, which is at fifth subframe with a periodicity of 80 milliseconds. The location of legacy SIB-1 in frequency domain is not fixed and is addressed by Physical Downlink Control Channel (PDCCH) in common search space which is decoded by the UE using System Information Radio Network Temporary Identifier (SI-RNTI). However, the victim UE in the dominant co-channel interference region with Primary broadcast channel (PBCH) Interference Cancellation (IC) capability may successfully acquire legacy MIB; otherwise fail to acquire the legacy MIB if it does not have PBCH IC capability. However, the victim UE may fail to acquire SIB-1 unless the transmitted SIB-1 coincides with the ABS of the aggressor cell.
Existing methods fail to provide mechanisms to ensure acquisition of system information by the victim UE in the dominant co-channel interference region of the victim cell and hamper the system information reception reliability of the victim UEs.